Great Barrier reef

Coral reefs get their genetic revolution

Using genetic tools, it's now possible to predict which corals will survive bleaching events.

Scientists have concocted many schemes to save coral reefs from climate change. Assisted migration. Selective breeding. Manipulating the coral microbiome.


Many of these conservation techniques are risky and unproven, but the stakes are high; the United Nations Intergovernmental Panel on Climate Change predicts that with a 2˚C increase in global temperatures, 99 percent of corals will be lost to bleaching.

"We are desperate," Mónica Medina, a coral reef biologist at Penn State University, told EHN.

There's a glimmer of good news. A new study published yesterday in Science offers a new roadmap for coral conservation using the tools that have revolutionized our understanding of the human genome. With cutting-edge genetics, it's now possible to predict which corals will bleach and which ones won't.

"That's a great asset to conservation efforts," Stephen Palumbi, a coral reef biologist at Stanford University who was not involved with the study, told EHN.

The effort is a fruitful symbiosis between population geneticists and coral biologists.

Marine heatwaves devastate reefs, causing coral polyps to eject the symbiotic algae that live within their tissues. Without their photosynthesizing tenants to make sugars and nutrients, the polyps starve. But some corals can weather the heat, and hold onto their symbionts—a trait that turns out to be largely heritable.

By propagating branches from these survivors it's possible to selectively breed heat tolerant individuals, and use them to repopulate reefs.

This strategy has an obvious drawback: we only know which corals are hardy after everything else dies. But if you can screen for that adaptation in a coral's genome, "you don't have to wait for mass bleaching events to reveal these tolerant corals," Zachary Fuller, a population geneticist at Columbia University and lead author of the study, told EHN.

Banner photo: Coral reef in the Maldive Islands. (Credit: Ahmed Areef/Unsplash)

The stony coral Acropora millepora breeds with its neighbors, but scatters its infant polyps to the currents, which can carry them for miles. At the height of a mass bleaching event in the Great Barrier Reef in 2017, researchers in Australia collected samples from more than 200 colonies of A. millepora in different parts of the reef. It's the largest population sample in any coral study to date.

Mapping the complete genomes of hundreds of coral colonies would be prohibitively expensive, but Fuller's team used a shortcut that brings down the cost.

"They have built the best coral genome that anybody's ever built at the chromosome level," said Palumbi. Using that genome as a reference, the team then skimmed the rest of the samples for random genetic sequences and filled in the gaps.

Of course, corals are doubly complicated creatures. The researchers sequenced the genome of the symbiotic algae, as well.

Drawing on environmental data collected from the reef, and observations of bleaching variation among their samples, the team searched for associations between the corals' genes and heat tolerance.

They found the bleaching response isn't controlled by one gene, as some have hoped, but probably by many. That makes heat tolerance in corals "a lot more akin to say, human diabetes, or even human height, where there are lots of genes involved," said Palumbi.

Human genetic studies draw on thousands of genomes. So Fuller and his team were excited to find that with only 200 samples, their model could explain roughly 60 percent of the variation in bleaching. With more samples, the picture will only grow sharper.

"Our goal is to start applying these types of approaches into other species that are at risk of climate change," said Fuller.

"It's worked in agriculture, and it's worked in human disease," said Medina. "Working with what nature has already given us" is "a pretty good bet, a safe bet."

It's a steady step forward, but the fanciest genomics won't save the Great Barrier Reef if we can't reign in the warming trend, said Palumbi.

"The reason to be so interested and excited about it, and go for it, is that it gives us the chance to save as much as possible for the next couple of decades while we actually get a grip on carbon dioxide emissions and bring them way down."

Banner photo: Clown fish on a coral reef in the Great Barrier Reef, Queensland, Australia. (Credit: Giorgia Doglioni/Unsplash)

Ornate Parliament Hill building and clock tower in Canada's capital city.

Mark Carney’s rise places Trump between two quiet climate champions

Canada’s newly elected Prime Minister Mark Carney and Mexican President Claudia Sheinbaum, both seasoned climate advocates, now flank President Trump, creating a North American dynamic where climate leadership persists even when it’s not a campaign focus.

Justin Worland reports for TIME.

Keep reading...Show less
A kitchen wall with cabinets and an oven
Credit: Ida/Pixabay

Energy Star program faces shutdown as EPA reorganizes under Trump administration

The U.S. Environmental Protection Agency plans to eliminate the Energy Star program and other climate initiatives as part of a major agency reorganization, according to internal documents and recordings.

Lisa Friedman and Rebecca F. Elliott report for The New York Times.

Keep reading...Show less
Two men holding rope and setting up a roof for solar panels.

Political shifts stall $8 billion in clean energy projects as U.S. renewables boom

The U.S. clean energy sector has grown dramatically, but policy uncertainty under President Trump has already led to the cancellation or downsizing of nearly $8 billion in renewable projects this year.

Ames Alexander reports for Floodlight.

Keep reading...Show less
Sign in front of electric vehicle chargers that says 'Electric Vehicle Only'.

Why some House Democrats helped block California’s 2035 gas car ban

Thirty-five House Democrats joined Republicans to overturn California’s plan to phase out gas-powered cars by 2035, citing concerns about affordability and heavy industry lobbying.

Lisa Friedman reports for The New York Times.

Keep reading...Show less
Mining excavator in a mine pit.

Trump administration accelerates Alabama coal expansion mostly for foreign steel markets

The Trump administration is expediting the approval of a major Alabama coal mine expansion despite environmental and safety concerns, with most of the coal destined for export to foreign steelmakers.

Lee Hedgepeth reports for Inside Climate News.

Keep reading...Show less
LNG storage tank with a red sky in the background.

Louisiana expands LNG exports as Trump fast-tracks new terminal permits

A new liquefied natural gas (LNG) terminal is moving forward in southwest Louisiana, adding to the state’s growing LNG footprint as federal and state officials push for more fossil fuel infrastructure.

Tristan Baurick reports for Grist.

Keep reading...Show less
Big Ben and Parliament building in the United Kingdom.

UK residents take government’s climate strategy to European human rights court

Two British men argue that the UK’s failure to protect them from climate-related harm violates their human rights and have escalated their case to Europe’s top human rights court.

Damien Gayle reports for The Guardian.

Keep reading...Show less
From our Newsroom
Multiple Houston-area oil and gas facilities that have violated pollution laws are seeking permit renewals

Multiple Houston-area oil and gas facilities that have violated pollution laws are seeking permit renewals

One facility has emitted cancer-causing chemicals into waterways at levels up to 520% higher than legal limits.

Regulators are underestimating health impacts from air pollution: Study

Regulators are underestimating health impacts from air pollution: Study

"The reality is, we are not exposed to one chemical at a time.”

Pennsylvania governor Josh Shapiro speaks with the state flag and American flag behind him.

Two years into his term, has Gov. Shapiro kept his promises to regulate Pennsylvania’s fracking industry?

A new report assesses the administration’s progress and makes new recommendations

silhouette of people holding hands by a lake at sunset

An open letter from EPA staff to the American public

“We cannot stand by and allow this to happen. We need to hold this administration accountable.”

wildfire retardants being sprayed by plane

New evidence links heavy metal pollution with wildfire retardants

“The chemical black box” that blankets wildfire-impacted areas is increasingly under scrutiny.

Stay informed: sign up for The Daily Climate newsletter
Top news on climate impacts, solutions, politics, drivers. Delivered to your inbox week days.